Ultrasonic motor having a vibratory body and method of producing the same

ABSTRACT

An ultrasonic motor with a vibratory body which has plural groove groups formed in a surface of the vibratory body. Each groove group has at least two grooves which are formed parallel to one another. If the vibratory body has an annular shape, a groove forming member having as many cutting members as grooves in each groove group moves in a radial direction of the vibratory body while the cutting members rotate, simultaneously cutting each groove of a groove group in the surface of the vibratory body. When advancing vibratory waves are generated in a circumferential direction of the vibratory body, the state of vibration of the grooves in a groove group differs, and the resonance of the grooves is suppressed. If the vibratory body has a linear shape, the cutting members rotate as the groove forming member moves perpendicular to the vibratory body, simultaneously cutting each groove of a particular groove group.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ultrasonic motor having a vibratorybody and, more particularly, to an ultrasonic motor having a vibratorybody in which the configuration of grooves formed in the vibratory bodyand a method of forming the grooves in the vibratory body have beenimproved.

2. Description of the Related Art

Ultrasonic motors have been disclosed, for example, in JP-B-1-40597(Japanese Examined Patent Publication 1-40597). This kind of ultrasonicmotor has a pressure welded vibratory body and a moving body. Apiezoelectric body, for instance, which generates vibrations, is mountedin the vibratory body, and by being excited, gives rise to travelingvibratory waves. The moving body is frictionally driven by means ofthese vibratory waves.

This kind of ultrasonic motor results in achieving high torque even whenoperating at low speed, and is put to practical use in variousmechanisms of cameras, etc.

FIG. 9 is a plan view showing one example of the vibratory body of aprior art ultrasonic motor. As shown in FIG. 9, the vibratory body 10has an approximately annular shape, and plural grooves 11 are formed inits surface along the circumferential direction. These grooves 11 areformed in order to increase the amplitude of the vibration of thevibratory body 10. The grooves 11 are directed approximatelyperpendicular to the direction of advance (circumferential direction) ofthe vibratory waves, or in other words, are formed so as to be directedin radial directions of the vibratory body 10. Namely, as shown in FIG.9, the grooves 11 are formed parallel with respect to lines I--I, II--IIextending in the radial direction and passing through the axis (centralportion) of the vibratory body 10.

The grooves 11 of the vibratory body 10 are formed one at a time by agroove forming member comprising a grindstone, etc., which revolves inorder to successively cut into the surface of the vibratory body 10.Approximately 100 grooves are generally formed in the vibratory body 10.

However, in the above ultrasonic motor, when vibrational waves aregenerated in the vibratory body 10, resonance of the grooves may occur.As a result of this resonance, anomalous sounds are generated during thedriving of the ultrasonic motor.

In addition, in the prior art method of preparing the vibratory body ofthe ultrasonic motor, as described above, an excessive amount of time isrequired to prepare the grooves of the vibratory body 10 because thegrooves 11 are formed one by one, resulting in a high manufacturingcost.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to reduce thegeneration of anomalous sounds during driving of the ultrasonic motor byimproving the shape of the grooves of the vibratory body of theultrasonic motor, by suppressing the resonance of the grooves whenvibrational waves are generated in the vibratory body.

It is a further object of the present invention to shorten the timerequired to prepare the grooves by means of improvements in theformation of the grooves of the vibratory body of the ultrasonic motorin order to reduce manufacturing costs.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part, will be obvious fromthe description, or may be learned by practice of the invention.

The foregoing objects of the present invention are achieved by providingan ultrasonic motor having an annular vibratory body with plural groovesdisposed side by side in an end and about the circumference of thevibratory body, such that the plural grooves form groove groups, eachgroove group having a first groove and a second groove formed adjacentto and parallel with one another.

In order to achieve the above objects, the groove groups of thevibratory body of the ultrasonic motor may have groove depths whichdiffer from one another. Also, the depths of the first groove and thesecond groove may differ from one another. By forming grooves havingdifferent depths in the vibratory body, the state of vibration of eachgroove can differ when vibrational waves are generated, suppressing theresonance of the grooves.

The above objects are further achieved by a method of preparing avibratory body of an ultrasonic motor wherein an annular body is fixedto a support table, a groove forming member with at least two cuttingmembers of circular shape and spaced side by side at a predeterminedspacing, is moved in a radial direction of the annular body, the cuttingmembers rotate and cut into the annular body, to form a vibratory bodyof an ultrasonic motor from the annular body, by simultaneously formingplural grooves in an end surface of the annular body, and the supporttable is rotated through a predetermined angle, to set the position ofthe annular body with respect to the groove forming member.

In order to control the depth of cut that the groove forming membermakes with respect to the annular body, the groove forming member andannular body are moved in relation to each other.

While making the cuts to form the grooves, the groove forming member maybe moved from the outer ring side to the inner ring side of the annularbody. An alternative is to move the groove forming member from the innerring side to the outer ring side of the annular body. And still anotheralternative for making the grooves is by moving the groove formingmember from the outer ring side of the annular body via the centerportion of the annular body to the outer ring side of the opposite sideof the annular body.

In order to achieve yet another object of the present invention, amethod of preparing a vibratory body of an ultrasonic motor isperformed, wherein a linear body is fixed to a support table, a grooveforming member with at least two cutting members of circular shape andspaced side by side at a predetermined space, is moved perpendicular tothe linear body, and the cutting members rotate and cut into the annularbody, to form a vibrator), body of an ultrasonic motor frown the linearbody, by simultaneously forming plural grooves in the surface of thelinear body. Subsequently, the support table is moved a predeterminedamount, to adjust the position of the linear body relative to the grooveforming member, thereby allowing the groove forming member to cut moreplural grooves in the surface of the linear body. Each of the pluralgrooves simultaneously cut into the aforementioned linear body isparallel to one another. In preparing the vibratory body of anultrasonic motor, at least two parallel grooves are simultaneouslyformed by the groove forming member. Accordingly, the time for preparingthe grooves can be shortened.

Furthermore, when the groove forming member moves from the outer ringside of the annular body via the centered position of the annular bodyto the outer ring side of the opposite side of the annular body, aplurality of grooves can be formed on the opposite side of the annularbody by one continuous movement of the groove forming member.Accordingly, the preparation of the grooves becomes more efficient.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe preferred embodiments, taken in conjunction with the accompanyingdrawings of which:

FIGS. 1A and 1B are a plan view and an oblique view, respectively,showing an example of a vibratory body of an ultrasonic motor accordingto a first embodiment of the present invention.

FIG. 2 is an oblique view showing an example of a groove forming memberused to form groove groups of the vibratory body of FIG. 1.

FIG. 3 is an oblique view showing conditions during the formation of agroove group in the vibratory body by means of the groove forming memberof FIG. 2.

FIG. 4 is a flow chart illustrating the process of preparing the groovegroups of the vibratory body in accordance with the first embodiment ofthe present invention.

FIG. 5 is a plan view showing the direction of motion of the grooveforming member with respect to the vibratory member in accordance withthe first embodiment of the present invention.

FIG. 6 is an oblique view showing an example of a vibratory body of anultrasonic motor according to a second embodiment of the presentinvention, and of a groove forming member forming the vibratory body.

FIG. 7 is an oblique view showing an example of a vibratory body of anultrasonic motor according to a third embodiment of the presentinvention, and of a groove forming member for forming the vibratorybody.

FIG. 8 is an oblique view showing an example of a vibratory body of anultrasonic motor according to a fourth embodiment of the presentinvention, and of a groove forming member forming the vibratory body.

FIG. 9 is a plan view showing an example of a prior art vibratory body.

FIG. 10 is an oblique view showing an example of a vibratory body of anultrasonic motor according to a fifth embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings, wherein like reference numerals refer tolike elements throughout.

FIGS. 1A and 1B are a plan view and an oblique view, respectively, of anexample of a vibratory body of an ultrasonic motor according to a firstembodiment of the present invention.

As shown in FIGS. 1A and 1B, the vibratory body 20, similar to thevibratory body 10 which has been shown for the prior art in FIG. 9, isformed with an approximately annular shape, and plural groups 25 ofgrooves are formed at spacings along its circumferential surface. Thesegroups 25 of grooves comprise pairs of mutually parallel grooves 21 and22. These grooves 21 and 22 are formed parallel to lines I--I, II--IIextending in radial directions of the vibratory body 20 through thecenter portion of the groove group 25. Accordingly, the grooves 21 and22, differing from the grooves 11 of the vibratory body 10 of FIG. 9,are respectively not directed in the radial directions of the vibratorybody 20.

FIG. 2 is an oblique view showing an example of a groove forming memberused to form the groove groups 25 of the vibratory body 20. As shown inFIG. 2, groove forming member 30 has a pair of cutting members 31 and32, such as grindstones or the like, formed with an approximatelycircular shape and able to grind or cut. A spacer 35 is arranged betweenthe cutting members 31 and 32, in order to precisely position themparallel to each other at a suitable spacing. Moreover, holders 36a and36b are arranged on the outer sides of the cutting members 31 and 32 inorder to support them.

FIG. 3 is an oblique view showing the conditions when a groove group 25is being formed in the vibratory body 20 by the groove forming member30. As shown in FIG. 3, the vibratory body 20 is positioned on a supporttable 41 and, furthermore, is immovably held by a clamp 42. The supporttable 41 is rotatably supported.

Moreover, the groove forming member 30 is located so that its rotaryshaft is directed perpendicular to the axial direction of the vibratorybody 20, and is supported so that cutting members 31 and 32 can rotate(direction A in the Figure), and that respective motions are possible,in the vicinity of the vibratory body 20, such as a separating motion(direction B in the Figure) and a linear motion radial to the vibratorybody 20 (direction C in the Figure).

FIG. 4 is a flow chart illustrating the process of forming a groovegroup 25 in the vibrator), body 20. An example of the method ofpreparing the vibratory body 20 will be described below, based on FIGS.3 and 4.

Firstly, in step S1 of FIG. 4, preparation of a groove group 25 iscommenced. At this time, the count number Z, for counting the number ofgroove groups 25 formed in the vibratory body 20 in FIG. 3, is set to 0(initialization). Next, proceeding to step S2, the cutting members 31and 32 of the groove forming member 30 of FIG. 3 are driven by a driveunit (not shown in the drawing) and rotate in the direction A1 in FIG.3. At this time, the groove forming member 30 is on the right hand sideof the vibratory body 20 of FIG. 3, in a state spaced apart from thevibratory body 20.

Next, in step S3 of FIG. 4, the groove forming member 30 is moved at asuitable speed of movement in the radial direction (direction C1 in FIG.3) of the vibratory body 20. Thus the surface of the vibratory body 20is cut and a groove group 25 is formed (step S4 in FIG. 4). Grooves 21and 22 are simultaneously formed.

When the formation of the groove group 25 ends, proceeding to step S5 ofFIG. 4, the groove forming member 30 is returned to its initialposition. Namely, in FIG. 3, the groove forming member 30 is moved inthe direction B2, removing it from cutting the vibratory body 20 and, inaddition, is moved in the direction C2 in FIG. 3, and is returned to itsinitial position as in step S1.

Next, proceeding to step S6 of FIG. 4, the count number Z is incrementedby 1, and then proceeds to step S7. In step S7, it is determined whetherthe count number Z has reached the total number X of groove groups to beformed in the vibratory body 20. When the count number Z has reached thenumber X of groove groups, it is determined that the formation of groovegroups 25 in the vibratory body 20 has ended, and proceeding to stepS10, the preparation of additional groove groups 25 ends.

When the count number Z in step S7 has a smaller value than the number Xof groove groups 25, the routine next proceeds to step S8. In step S8,the support table 41 is rotated through a predetermined angle, namely by(360/X)°. In this manner, the vibratory body 20 is set in a positionwith respect to the groove forming member 30 for the formation of thenext groove group 25.

Next, proceeding to step S9, the adjustment of the cutting depth of thegroove forming member 30 is performed. Because the abrasive grains ofthe surfaces of the cutting members 31 and 32 of the groove formingmember 30 appropriately wear away during the cutting of the grooves, andnew cutting edges are successively formed as a consequence of making thegroove groups 25, the size of the external diameter gradually decreases.Accordingly, a correction of this amount is performed. Moreover, whenthe reduction in size of the external diameter of the cutting members 31and 32 is slight, the process of step S9 may be bypassed. The adjustmentof the cutting depth is performed by means of a suitable amount ofmovement of the groove forming member 30 in the direction B1 in FIG. 3.When this adjustment ends, returning to step S3 from step S9, theformation of a new groove group 25 is performed.

FIG. 5 is a plan view showing the direction of movement of the grooveforming member 30 with respect to the vibratory body 20. In the abovementioned method of preparation, the groove forming member 30 is movedin the direction C shown in FIG. 5 (from the outer ring side to theinner ring side of the vibratory body 20), but the motion is not limitedto this; the groove forming member 30 can be moved in the direction Dshown in FIG. 5 (from the inner ring side to the outer ring side of thevibratory body 20). Another possibility is to move the groove formingmember 30 in the direction E in FIG. 5 (the groove forming member 30 ismoved from the outer ring side to the inner ring side of the vibratorybody 20, and furthermore across the center portion of the vibratory body20 to the outer ring side on the opposite side of the vibratory body20).

When vibratory waves are generated which advance in a circumferentialdirection of the vibratory body 20 formed in this manner, each groove 21and 22 vibrates. Here, the grooves 21 and 22 are not exactly radial but,instead, are slightly offset from the radial direction of the vibratorybody 20, the orientations of the grooves 21 and 22, respectively, aredifferent with respect to the direction of advance of the vibratorywaves and, as a result, the same vibration does not occur in each of thegrooves 21 and 22. Because of this, the resonance of each groove 21 and22 due to the vibratory wave can be controlled.

FIG. 6 is an oblique view showing an example of a vibratory body of anultrasonic motor and of a groove forming member for its formation,according to a second embodiment of the present invention. In otherfollowing embodiments described below and shown in the correspondingfigures, portions which are the same as in the first embodiment examplebear the same reference symbols, and duplicate descriptions areappropriately omitted.

In the vibratory body 20A shown in FIG. 6, each groove group 25acomprises a pair of grooves 21a, 22, which are formed parallel to eachother, similar to the groove groups 25 of the vibratory body 20 shown inFIG. 1, along an end surface and in a circumferential direction of thevibratory body 20. Here the depth of the grooves 21a is formed deeper byδ than the depth of the grooves 22.

In order to form the groove group 25a, instead of employing the cuttingmember 31, a cutting member 31a, which is larger by 28 than the cuttingmember 31 of the first embodiment (FIG. 3), is set up in a grooveforming member 30A. Accordingly, the groove 21a is formed by the cuttingmember 31a, and simultaneously, the groove 22 is formed by means of thecutting member 32.

FIG. 7 is an oblique view showing an example of a vibratory body of anultrasonic motor and of a groove forming member for its formation,according to a third embodiment of the present invention. In contrast tothe groove group 25 of the vibratory body 20 of FIGS. 1A and 1B and thegroove group 25a of the vibratory body 20A of FIG. 6, each of whichcomprise two grooves, the groove group 25b of the vibratory body 20Bshown in FIG. 7 comprises three grooves 21-23, formed simultaneously andmutually parallel. The groove 22 is located in the center of the groovegroup 25b, and is directed in the radial direction of the vibratory body20B. The other two grooves 21 and 23 are offset slightly from the radialdirection of the vibratory body 20.

Moreover, in order to form the groove group 25b, an additional cuttingelement 33 is set up in the groove forming member 30B, in comparisonwith the groove forming member 30 of FIG. 2. Furthermore, the cuttingmembers 31 and 32, and the cutting members 32 and 33, are spaced apartat appropriate respective spacings by respective spacings 35a and 35b,and are positioned parallel to each other, in order to cut parallelgrooves 21, 22 and 23.

FIG. 8 is an oblique view showing an example of a vibratory body of anultrasonic motor and of a groove forming member for its formation,according to a fourth embodiment of the present invention. The vibratorybody 20C shown in FIG. 8, similar to the vibratory body 20B of FIG. 7,has groove groups 25c each comprising three grooves 21a, 22, and 23a,formed mutually parallel to one another. The groove depth of the twoside grooves 21a and 23a within groove group 25c is formed deeper thanthe groove depth of the center groove 22.

The groove forming member 30C is set up with cutting members 31a, 32 and33a. The cutting members 31a and 33a of the groove forming member 30Chave an external diameter which is greater than that of the respectivecutting members 31 and 33 of the groove forming member 30B of FIG. 7.Accordingly, the grooves 21a, 22 and 23a are simultaneously formed bythe cutting members 31a, 32 and 33a, respectively, to produce each ofthe groove groups 25c.

In the vibratory bodies 20A-20C of the above second through fourthembodiments, by means of the respective groove forming member 30A-30C,grooves can be formed by a method of processing similar to that of thefirst embodiment shown in FIGS. 3 and 4.

In the vibratory bodies 20A and 20C, the direction of each groove of therespective groove groups 25a and 25c is parallel to each other, and inaddition to this, the depth of the grooves vary. Accordingly, when eachgroove is vibrated by the vibrational wave, because the amplitudes ofvibration of the grooves differ, the resonance of the groups canfurthermore be controlled.

Various embodiments of vibratory bodies of ultrasonic motors and ofgroove forming members for their formation, according to the presentinvention, have been described above, but the present invention is notlimited to the above mentioned embodiments, and various modificationsare possible within the scope of the present invention without departingfrom its essentials. For example, as previously described, the groovegroups 25 were formed by a single cut of the groove forming member 30.But depending upon the materials of the cutters 31 and 32 and of thevibratory body 20, the depth of the grooves to be cut into the vibratorybody 20 by the groove forming member 30, and the speed of rotation ofthe cutters 31 and 32 or speed of movement of the groove forming member30, the groove groups may also be formed by repetitive movement of thegroove forming member 30 while gradually making the cutting depth deeper(and similarly in the second through the fourth embodiment examples).

In the above-described embodiments, each groove 21a and 22 (or 21a, 22and 23a) of the groove groups 25a (or 25c) may be formed with adifferent groove depth. Furthermore, each groove group 25a (or groovegroup 25c) may be formed with a different groove depth relative to othergroove groups 25a (or groove group 25a).

FIG. 10 is a front view showing a vibratory body of an ultrasonic motorand of a groove forming member for its formation, according to a fifthembodiment of the present invention. In the first through fourthembodiments, the vibratory bodies 20 and 20A-20C are approximatelyannular in shape, but as shown in FIG. 10, a vibratory body 20D has alinear form. Grooves 21 and 22 of groove group 25 can be simultaneouslyformed in the vibratory body 20D using a groove forming member 30, whichcan be the same as the one used in the first embodiment, by cutting thevibratory body 20D at a predetermined spacing or an optional spacing.Furthermore, the vibratory body 20D is moved by a predetermined amountin the direction F in FIG. 10, and successive groove groups 25 can beformed.

Moreover, by using the groove forming members 30A, 30B, or 30C, groovegroups 25a, 25b, or 25c can be formed in the vibratory body 20D.

As a result of the above-described embodiments of the present invention,grooves, formed in an end of a vibratory body of an ultrasonic motor andwithin a given groove group, are parallel to one another, and becausethe state of vibration of each groove differs when vibratory waves aregenerated in the vibratory body, resonance of the grooves can besuppressed. In addition, by having grooves of different depth, theamplitudes of vibration of each groove differ from one another when thevibratory waves are generated, thereby further suppressing the resonanceof each groove. In this manner, the generation of anomalous soundsduring the driving of the ultrasonic motor is reduced.

Also as a result of the above-described embodiments of the presentinvention, the time required to make the grooves in the vibratory bodyis reduced, which in turn reduces the cost of manufacture of theultrasonic motor.

Although a few preferred embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. An ultrasonic motor comprising:a vibratory bodyhaving an annular configuration and a top surface of said annularvibratory body; and a plurality of groove groups formed in the topsurface side by side in a circumferential direction, each groove grouphaving a first groove and a second groove adjacent to and parallel toone another.
 2. The ultrasonic motor as claimed in claim 1, wherein saidplurality of groove groups comprise:a first groove group; and a secondgroove group having corresponding first and second grooves withdifferent depths than corresponding first and second grooves of saidfirst groove group.
 3. The ultrasonic motor as claimed in claim 1,wherein said first and second grooves of the same groove group havedifferent depths from one another.
 4. The ultrasonic motor as claimed inclaim 2, wherein said first grooves of said first and second groovegroups have different depths than said second grooves of the same groovegroup.
 5. The ultrasonic motor as claimed in claim 1, wherein eachgroove group further comprises:a third groove adjacent to said secondgroove and parallel to said first and second grooves of the same groovegroup.
 6. The ultrasonic motor as claimed in claim 5, wherein saidplurality of groove groups comprise:a first groove group; and a secondgroove group having corresponding first, second and third grooves withdifferent depths than corresponding first, second and third grooves ofsaid first groove group.
 7. The ultrasonic motor as claimed in claim 6,wherein said first and third grooves have different depths from saidsecond groove.
 8. The ultrasonic motor as claimed in claim 7, whereinsaid first grooves of said first and second groove groups have differentdepths than said second grooves of the same groove group.